Economical High Pressure Wear Resistant Cylinder That Utilizes A High Pressure Field For Strength

ABSTRACT

A high-pressure wear resistant cylinder that utilizes a high-pressure field for strength is an economical method of, or device for, handling very high pressures and the pumping of abrasive and corrosive fluids. The economic considerations are so favorable, that the invention may be considered a replacement part. The invention is suitable for a variety of applications, particularly a reciprocating flow work exchanger in the well stimulation or hydraulic fracturing industry. Using a high pressure field to strengthen the external surface (outside) of a pipe that is precision honed and plated or sleeved internally (inside), it is now possible to construct various high pressure machines in a relatively inexpensive manner. This invention makes it possible to use pipe with internal operating pressures greater than their nominal operating pressure ratings permit. This invention will be used in various high pressure piping and machinery applications.

CROSS-REFERENCE TO RELATED APPLICATION

The present patent application is based upon and claims the benefit of provisional patent application No. 62/106,668, filed on Jan. 22, 2015

BACKGROUND OF THE INVENTION

Hydraulic fracturing (also hydrofracturing, hydrofracking, fracking or fraccing), is a well-stimulation technique in which rock is fractured by a hydraulically pressurized liquid made of water, sand, and chemicals. Some hydraulic fractures form naturally—certain veins or dikes are examples. A high-pressure fluid (usually chemicals and sand suspended in water) is injected into a wellbore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine will flow more freely. When the hydraulic pressure is removed from the well, small grains of hydraulic fracturing proppants (either sand or aluminum oxide) hold the fractures open. Traditionally, the fracking fluid (including proppants) is delivered to the well with powerful and expensive reciprocating plunger pumps. The pressure required to fracture these formations ranges can exceed 15,000 psi.

High pressure pump failures are the number one operational challenge faced by the industry. The challenges faced include the following:

1. High pump maintenance costs

2. Sporadic and excessive downtime (pump failures)

3. High levels of redundancy (mitigate pump failures)

These challenges are all due to the pumping of abrasive and highly viscous frac fluids. It is the equivalent of adding sand to your car's engine. The best way to improve the above problems is to avoid sending the fracking fluid through the high pressure plunger pumps. Plunger pumps that pump or move clean and ph neutral fluids last longer, are more economical to operate, and require less maintenance.

Industry professionals are currently evaluating different methods of delivering the fracking fluid to the well (borehole) at the required pressures with newly developed or modified devices other than traditional reciprocating plunger pumps.

If these new technologies are able to move the fracking fluid with new and more robust equipment, the industry will experience a paradigm shift. The primary benefits will be reduced maintenance costs, decreased pump redundancy, and lower capital expenditures. Any new technologies must improve the total cost of owning and operating the equipment that transports the fracking fluid and proppants at high pressure into the well. These new technologies must be in-expensive to manufacture, easy to service, and economical to maintain with affordable spare parts (wear items).

Two new ideas concerning the delivery of the fracking fluid into the well without sending the fracking fluid through the high pressure plunger pump are being explored. Both of these potential solutions rely upon new machines that are conceived from fluid transfer equipment originally developed for low pressure and highly filtered fluid applications such as reverse osmosis desalination. One approach is to use a modified rotating pressure exchanger energy recovery unit and the other is a reciprocating dual work exchange energy recovery unit. Again, both of these new ideas/new pumping machines are based on experience gained in handling very clean filtered water at low pressure (rarely exceeds 1200 psi), and with pH values not far from neutral.

This invention is applicable to many different industries. Of the numerous industries being evaluated, it appears that the fracking industry may benefit the most at this time. For this reason, this description will reference a reciprocating dual work exchange unit to help explain a practical application of subject invention.

In designing and constructing a reciprocating dual work exchanger for handling high pressure and abrasive fluids such as fracking fluid, complex challenges arise. Of several challenges, two of the biggest are working with high pressure and abrasive fluids including but not limited to water, sand, aluminum balls, acid and corrosion inhibitors.

Also of significance, is the fact that the reciprocating dual work exchanger's total cost of ownership (purchase price of an asset plus the costs of operation) must be more favorable than the current methods. This invention makes the design, production, operation, and ownership of a fracking work exchanger and other products economically feasable.

SUMMARY OF THE INVENTION

The invention is based upon a pipe, tube, or pressure vessel located within another pressure containing vessel such as a pipe, tube or other similar form. The cavity between the inner wall of the outer vessel and the outer wall of the inner vessel is pressurized. In this way, the inner vessel or pipe can be much lighter and less expensive because the inner pipe is no longer required to withstand the required working pressure of the inner pipe alone. This invention relies upon the creation of a pressure field to support the demand placed on the internal pipe or pressure vessel. For example, if a pipe that is expected to wear-out frequently, must safely operate at 10,000 psi, this invention makes it possible to construct an outer vessel rated to 10,000 psi, place an internal pipe of vessel rated for only 5,000 psi and charge the space between the two up to 5,000 or 6,000 psi, thus reaching the desired 10,000 psi. This allows the inner pipe to absorb all wear and to be constructed of cheaper and lighter material. The expensive outer vessel does not see any wear. The inner tube or vessel is mounted in a way to allow of easy and quick replacement.

To design a reciprocating work exchanger pumping machine, the diameter of the barrel, the length of the barrel, and the speed at which the plunger/piston will travel must be established. These three factors define the capacity (or how much fluid the pumping machine can move) of the work exchanger. The capacity is expressed in terms of a volume unit per time unit such as liters per minute (Ipm) or gallons per minute (gpm).

Next, consideration must be given to what fluid is being pumped so that a suitable piston seal material can be selected. In the case of very abrasive fracking fluid a good choice for a piston seal would be high-intensity acrylonitrile butadiene rubber or NBR. The reciprocating plunger needs to seal tightly against the walls of the work exchanger just as the piston in our syringe must seal against the walls of the syringe barrel or the fluid can not be moved. Depending on the type of seal being used, the maximum speed of the reciprocating plunger (expressed in distance unit per time unit) will be defined. For example, if the seal is made of rubber and the speed is very high, the rubber will overheat and fail prematurely.

The length of the barrel is a design criteria established initially by the desired overall size of the work exchanger. For fracking applications, a length of ten feet is a good place to start. With this dimension, a finished work exchanger solution can be easily transported on a trailer from jobsite to jobsite.

Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawings.

IN THE DRAWINGS

FIG. 1 is a crosssection view of a reciprocating dual work exchanger having a high-pressure wear resistant cylinder that utilizes a high-pressure field to strengthen the inner vessel, based upon charging lines and an external pressure source such as a dedicated pressure circuit or pressure from the pressure source that drives the work exchanger.

FIG. 2 is a crosssection view of an alternative reciprocating dual work exchanger with a high-pressure wear resistant cylinder that utilizes a high-pressure field for strength based upon charging ports that use pressure from the pressure work exchanger itself.

FIG. 3 is a crosssection view of an alternative reciprocating dual work exchanger with a high-pressure wear resistant cylinder that utilizes multiple high-pressure fields for strength based upon charging multiple ports and chambers that use pressure from the pressure work exchanger itself.

FIG. 4 is a crosssection view of an alternative reciprocating dual work exchanger with a high-pressure wear resistant cylinder that utilizes two high-pressure fields for strength based upon charging ports that use pressure from the pressure work exchanger itself.

FIG. 5 is a crosssection view of an alternative reciprocating dual work exchanger with a high-pressure wear resistant cylinder that utilizes a high-pressure field for strength based upon charging lines and an external pressure source such as a dedicated pressure circuit or pressure from the pressure source that drives the work exchanger. Different from figure one in the simple symmetrical design of the internal high-pressure tube.

FIG. 6 is a representation of a traditional work exchanger without a high-pressure wear resistant cylinder and without a high-pressure field for strengthening purposes.

FIG. 7 is a crosssection view of an alternative reciprocating dual work exchanger where the fluid end assembly has been replaced by a simpler system of check valves and isolation valves.

FIG. 8 is a crosssection view of an alternative reciprocating dual work exchanger without the fluid end assembly or system of check valves and isolation valves

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a reciprocating dual work exchanger is shown. The reciprocating dual work exchanger having a special high-pressure flange (1) that is connected to a main casing flange (2), which holds a support piece (3), for securing a high-pressure wear resistant cylinder (10) that utilizes a high-pressure field (7) for strength. The high-pressure field (7) is created between an outer pressure chamber (6) and the high-pressure wear resistant cylinder (10). The high-pressure field (7) may be fed with charging lines (5 and 8) together with an external pressure source (not shown) such as a dedicated pressure circuit or pressure from the source that drives the work exchanger. A piston (9) will move back and forth through the high-pressure wear resistant cylinder (10). The high-pressure wear resistant cylinder (10) is positioned and sealed in with positioning pieces (3 and 11) in the sealing region (4) through use of O-rings, gaskets or other methods suitable for handling the required system pressure (not shown). The outer pressure chamber (6) is connected to a fluid end assembly (40). The fluid end assembly contains a valve block (13) and a valve block carrier (12). The fluid end assembly (40) may be fabricated from individual components (12 and 13) which house the two check valves (30 and 32). Alternatively, the fluid end assembly (40) may be constructed of a single forging depending upon the desired pressure to be safely handled. The valve cover (34) of the valve block 13 may contain a special high-pressure flange (14) and an access cover (15) that allows the high-pressure wear resistant cylinder (10) and support piece (11) to be removed without disrupting/disconnecting any piping connected to the unit. A pressure gauge (20) is used to monitor pressure within the high-pressure field (7) at all times. Pressure gauge (20) may alternatively be an electronic sensor or other mechanical pressure-monitoring device.

The piston (9) is moved in one direction by pumping fluid into check valve 32. When fluid is pumped into the special high-pressure flange (1), the piston (9) moves in an opposite direction forcing the fluid out of the inner cavity and through the exit check valve (30).

Referring now to FIG. 2, an alternative reciprocating dual work exchanger is shown. The high-pressure field (7) is created/energized through charging ports (16) contained within the high-pressure wear resistant cylinder (10). The charging ports (16) use the pressure generated from the piston (9) and system pressure (not shown) that moves piston (9).

FIG. 3 is an alternative reciprocating dual work exchanger having the high-pressure wear resistant cylinder (10) that utilizes multiple high-pressure fields (19) for strength. The multiple high-pressure chambers (19) are energized/charged through a plurality of charging ports (17). The multiple high-pressure chambers (19) are created with a plurality of partitions (18) that use pressure from the piston (9) and system pressure that moves the piston (9).

FIG. 4 is yet another alternative reciprocating dual work exchanger. The pressure field (7) is created/energized through charging ports (16) that use pressure generated from the piston (9) and system pressure that moves the piston (9). A divider (21) is inserted in the high-pressure field (7) to created two individual pressure fields. The divider (21) is stationary in the preferred embodiment, but may move depending on the desired application. FIG. 5 is an alternative reciprocating dual work exchanger. FIG. 5 differs from FIGS. 1-4 in that the high-pressure wear resistant cylinder (10) is symmetrically designed with plain end to reduce production costs. This symmetrical design also allows the fluid end assembly (40) to be attached and removed in quicker and easier fashion, thus reducing down time. In FIG. 1, the high-pressure wear resistant cylinder (10) attaches to the fluid end assembly (40) at position 22 (shown on FIG. 5). Conversely, the high-pressure wear resistant cylinder (10) depicted in FIG. 5, attaches to the fluid end assembly (40) at seal point (4).

FIG. 6 is a representation of a traditional work exchanger without a high-pressure wear resistant cylinder (10) and without a high-pressure field (7) for strengthening purposes. Of importance is the friction between the piston (9) and the main pressure unit housing (6). As the piston (9) and housing (6) rub on each other through the reciprocating action, both components will wear and need to be replaced quickly in the abrasive and corrosive fracking industry. In this conventional design, the very expensive housing (6) will need to be replaced at prohibitive rate.

Referring now to FIGS. 6 and 7, an alternative reciprocating dual work exchanger is shown without the fluid end assembly (40) of FIG. 1. The fluid end assembly has been replaced in FIG. 7 by a simpler system comprising a primary seal cap (55) attached to a pump manifold (56) and pipe nipples (57). Isolation valves (58) are attached to control fluid flow. Check valve (59) controls the direction of fluid flow, preventing backflow. The check valves (59) are connected to the pipe nipple (57) with a union (60). A gasket may be used on piston 9 to create a better seal. FIG. 8 shows the reciprocating dual work exchanger without a fluid end assembly or a series of check valves and isolation valves. The pump manifold (56) is welded to the outer pressure chamber (6) at weld point (56). This allows the high-pressure wear resistant cylinder (10) to be removed at the opposite end.

Through use of this invention, the high-pressure wear resistant cylinder (10) utilizes the high-pressure field (7) for strength, and the method of installing, implementing, and manufacturing the reciprocating dual work exchanger for abrasive and corrosive application, such as fracking, becomes economically viable.

The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims. 

I claim:
 1. An apparatus for pumping fluid comprising: an inner cylinder defining an interior cavity and an exterior surface, an outer cylinder, encompassing the inner cylinder, having an interior surface and an exterior surface, the interior surface of the outer cylinder being in communication with the exterior surface of the inner cylinder, a means for sealing one end of the inner and outer cylinders, an end assembly fixed attached to the opposed end of the inner and outer cylinders for moving fluid into and out of the interior cavity of the inner cylinder, wherein the outer cylinder has a higher pressure rating than the inner cylinder, and provides greater structural integrity to the inner cylinder, and a piston located within the inner cylinder cavity for moving the fluid contained in the inner cavity.
 2. The apparatus of claim 1 wherein the interior surface of the outer cylinder is spaced apart from the exterior surface of the inner cylinder, and a pressure field is created between the exterior of the inner cylinder and the interior of the outer cylinder wherein pressurized fluid is added to increase the pressure capability of the inner cylinder.
 3. The apparatus of claim 2 wherein the pressure field is charged through ports contained in the inner cylinder.
 4. The apparatus of claim 2 wherein the pressure field contains a plurality of dividers creating a plurality of smaller pressure fields.
 5. The apparatus of claim 2 wherein the pressure field is charged through ports contained in the outer cylinder.
 6. The apparatus of claim 1 wherein interior surface of the outer cylinder is in direct contact with the exterior surface of the inner cylinder thereby providing greater structural integrity to the inner cylinder.
 7. An apparatus for pumping abrasive fluid comprising: an inner cylinder defining an interior cavity and a specified pressure rating, an outer cylinder defining an interior cavity and a second specified pressure rating which is greater than the pressure rating of the inner cylinder, a piston contained within the inner cylinder cavity for moving the fluid contained in the inner cavity, and wherein, the inner cylinder is fitted within the inner cavity of the outer cylinder, creating a pressure field between the exterior of the inner cylinder and the interior of the outer cylinder wherein pressurized fluid is added to increase the pressure capability of the inner cylinder
 8. An apparatus for pumping fluid comprising: an inner cylinder defining an interior cavity, an exterior surface, and a specified pressure rating, an outer cylinder, encompassing the inner cylinder, having an interior surface, an exterior surface, and a second specified pressure rating which is greater than the pressure rating of the inner cylinder, a piston located within the inner cylinder cavity for moving the fluid contained in the inner cavity, the interior surface of the outer cylinder is spaced apart from the exterior surface of the inner cylinder, and a pressure field is created between the exterior of the inner cylinder and the interior of the outer cylinder wherein pressurized fluid is added to increase the pressure capability of the inner cylinder. a means for sealing one end of the inner and outer cylinders, an end assembly fixed to the opposed end of the inner and outer cylinders for moving fluid into and out of the interior cavity of the inner cylinder, and wherein the outer cylinder, having a higher-pressure rating than the inner cylinder, provides greater structural integrity to the inner cylinder. 